old bolts

Narrowfarm · May 17, 2009

Hello i am replacing some of the 62 year old 3/4 inch inch diameter bolts in my tractor.Over time does the steel bolts become more weaker and prone to break easier???

John B. · May 17, 2009

I would think so but I'm not a metalurgist either. The metal was different back then though too!!

Joe(TX) · May 17, 2009

The metal does not change on its own due to age. It is affected by outside influence. Corrosion can weaken by reducing the size. Fatique caused by loading and unloading will cause the bolt to fail.
Older bolts had higher carbon content and were more brittle than newer alloy bolts. Newer grade bolts are easy to indentify by the grade marks on the heads.
Hope not to confuse, but the engineer in me comes out sometimes.

Russ from MN · May 17, 2009

If they are not rusted away or over stressed (how would you know) they should not have to be replaced, although what frustrates me is the odd sizes, recently took the bolts out of our 48 Farmall C draw bar, 3/4 bolt 1" head 1 1/16 nut! Used some of the wrenches that I wondered why my Dad had!

Anonymous-0 · May 17, 2009

The notch factor of threads, along with rust, can make old bolts weaker... JMHO, I am a machinist, not an Engineer..

37 chief · May 17, 2009

I always thought the old ones were better. You can be sure they were made in the USA. I have several 5 gal pales I need to sort sometime from tractors I have scrapped. Stan

Leroy · May 18, 2009

You would thik that the way some of the old bolts are rusted that they would never come loose but when you try them the threads come out looking like new and a 5 year old bolt is rusted so bad you have to cut the nut of to get it out.

CWL · May 18, 2009

I always thought the bolt and nut size was different so that a guy could work on his equipment with one wrench set.

GordoSD · May 18, 2009

Old bolts should not be reused. First, they could have been overstressed in tension, torsion, or compression. If they have just been normally stressed they can fail due to fatigue. Reaching their stress limit over and over they can be "work hardened" and more brittle.Corrosion can cause stress cracks, which will allow new stresses to build there.

Gordo (Former Aircraft Accident Investigator)

RAB · May 19, 2009

Not to be anti-engineers but sometimes those old bolts were so oversized and understressed that they may last another one hundred years or so.

Yes, they can become fatigued and stressed. Depends on the application, mode of possible failure (safe or dangerous), ease of later replacement, etc.

One thing is unlikely, and that is :- they will be stronger now than when they were in service 60 years ago.

Regards, RAB

old bolts

Narrowfarm

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John B.

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Joe(TX)

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Russ from MN

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Anonymous-0

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37 chief

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Leroy

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CWL

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GordoSD

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RAB

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